Automatic choke



May 16, 1939. HUNT 2,158,424

AUTOMATIC CHOKE -Filed Dc- 12, 1935 2 sheets shee l I v X 1551mm; 6 43929;; 32

INVENTOR. 76077- flU/Vr' BY 2 I TTORNEY.

S. F. HUNT AUTOMATIC CHOKE May 16, 1939.

2 Sheets-Sheet 2 Filed Dec. 12, 1935 INVENTOR .rco 77 f //z//v7- ATTORNEY Patented May 16, 1939 AUTOMATIC CHOKE Scott F. Hunt, Detroit, Mich" assignor to Milton E. Chandler, Detroit, Mich.

Application December 12, 1935, Serial No. 54,024

'7 Claims.

The object of this invention is to improve the starting means for automobile engines.

The method in common use heretofore has been to operate the choke valve manually. position of the choke valve being varied as the temperature of the engine varied. When starting cold more choking is required than when starting with a warm engine.

The problem is complicated by the fact that the moment the engine starts to fire it is desirable to immediately release the choke so as to admit airvfreely. However, if the choke is released entirely too much air is admittedand the engine stalls and must be re-started. Generally speak:- 1 ing, the two factors which determine starting are:

(a) The temperature of the air under the hood. (1)) The time the engine has been standing with the engine stopped A minor object of the invention is to permit the engine to be accelerated immediately after it is started. In order that a cold engine can be accelerated a considerable quantity excess fuel is required and I have invented means for supplying what I call an accelerating shot.

In solving the many inter-related problems involved in securing the above objects I have discovered that the resistance to the opening of the choke valve should decrease as the temperature of the engine increases and also as thetemperature of the air under the engine hood increases.

The resistance to the opening of the choke valve should decrease as the time in seconds during which the startingdevice is in operation increases. Finally, if the engine is immediately accelerated after being started, then there should be a momentary increase in resistance to the opening of the choke valve to permit what I term an accelerating fuel shot. In the figures:

Figure 1 shows my invention applied to a Figure 6 shows diagrammatically a partial plan view taken on plane 6-6 of Figure 4.

c In Figures 1, 2 and 3, a downdraft carburetor 55 20 is shown mounted on an inlet flange 29 connected to an inlet manifold 92 of an internal combustion engine which is shown at 60 in, Figure 4. An electro-magnetic solenoid 25 is mounted on the air entrance to the carburetor. In the center of the. solenoid is a core 24 adapted to be 5 moved by electricity which is permitted to flow around the solenoid. This core 24 acts as a piston and slides in the cylinder 3|. The flow of air into the piston is controlled by the check valve 26, which prevents the escape of air through the re- '10 stricted opening 32. This air leaks out of the cylinder 3| through the clearance between the piston 24 and the cylinder 3|. This'piston 24. is connected through a link 23 with a choke valve 22' which controls the air entrance to the car- 15 buretor. This valve may be loaded with a weight 2|, which weight will tend to open the valve.

In Figures 1 and 2 means are shown whereby when the choke valve is closed for starting, the throttle valve alsois slightly open. This is known 20 as the fast idle adjustment. The throttle is indicated by broken lines at H2, controlled by a throttle lever H3. A throttle stop I mounted on a throttle arm H5 engages with a cam I! I6.

- This cam is plvotally mounted on the body of the 5 carburetor and is moved by a lever H! which, in its turn, isconnected to the choke valve 22 through the link i It. When the choke valve is closed, the throttle H2 will be opened slightly to any desired degree, as determined by the cam 30 H6.

Three insulating blocks 50, 5| and 96 are adapted to be mounted on any convenient part of the engine. These blocks 50, 5! and 96 carry three thermostaticstrips 34, 35 and 94, which are 35 adapted to be deflected by heat. The thermostats 34, 35, carrying contacts 52 and 55, are shown in Figure 3. The contact 52 engages with another contact -shown diagrammatically by an arrow and numbered 4!. The contact 55 engages 40 with a similar contact marked by an arrow and numbered I02. The-third thermostat 94 mounted on an insulating block 96, carries a contact point 95, which engages with a conductor lfll.

When the temperature falls below 32 F., all

three contacts an: closed, that-is to say, .the contacts 52 and 55 are moved over to the left and contact 95 mounted on thermostat 54 is moved over to the right. Electric contacts. are

thus maintained between the conductor and the contact 52, between the/conductor I02 and thecontact 55, and between the conductor ml and the contact 95. This is the ooldcondition existing when starting an engine which has stood outside all night. 55

A battery 48 is shown connected, through a conductor 41, with an ignition switch 33 which controls the flow of electricity to an ignition circuit breaker, shown diagrammatically, by the cam I20 and the conductor I2I. Current also flows through the ignition switch 33 to the conductor 4| and-so to the contact 52, down through the thermostatic metal 3} (which short-circuits the resistance 48).

with the thermostat 35 which, in its turn, is connected through the conductors I02 and 51 with a conductor I0| which engages with the movable contact 95 mounted on the thermostat 94. The resistance 39 is interposed-in the connection between the conductor 51 and the conductor III and is short-circuited by the thermostat 94 when the contact .95 engages with the conductor I8I,

when the current fiows across a conductor 0.

which leads through a conductor III to the conductor 30. When the contact 95 is opened, how- 'ever, a small quantity of current can still flow from the conductor 51 to the conductor III, through the resistance 39. The conductor connects with the conductor 38 which leads back to the solenoid 25, and thusoperates the piston 24, as described above.

In'the box 59 mounted on the engine, there are two stationary terminals 531 and I04. The terminal 53 is connected with the conductor 30 and the terminal I84 is connected, through the conductor 99 and a heating coil 98, with the ground 14. The movable contact 38 is held in engagement with the stationary terminal 53 by a tension spring 43. In Figure 6, an alternative construction using a compression spring 43, is shown. This contact 38 is connected to a piston 31 which is loosely mounted in a cylinder 36, the cylinder being connected to the vacuum in the inlet manifold through the pipe 21. The other movable contact 38' is connected with a loosely fitting piston 31' which reciprecates in a cylinder 36' and is moved by a compression spring 43'. This cylinder is in communication with the atmosphere through an opening 91. The chamber I00 within the housing 59 contains the contacts 38, 38' and has an adjustable volume determined by the plug I86. When there is a vacuum in the mixture outlet, the pipe 21 communicates this vacuum to the cylinder 36. Then the contact 38 is drawn over to the left by the vacuum so communicated, which vacuum acts on the piston 31 and stretches the spring 43, and the circuit through 53, 38 is broken.

"At the same time, owing to theclearance between the piston 31 and the cylinder 36, a vacuum is created in the chamber I88 which, in'its turn, draws the contact 38 over to the right, the piston 31' compressing the spring 43 under the influence of the atmospheric pressure admitted The circuit through the contact 4| and the thermostats 34, 35, and 95, and the conductors III and 38, mrmits a certain amount of current to flow through the solenoid to maintain the choke valve in closed position after the circuit 38, 53 has been broken. The period of time that the current continues to flow freely through the circuit including the three thermostats, depends on the time it takes for the heating coil 98 to deflect the two thermostats 35 and 94 and to open the contacts 55, I02, and the contacts 95, IN. When these contacts open, the current is then forced to take another path and flows from the battery 48 through the switch 33 to the terminal 4|, the contact 52, through the thermostat 34, through the conductor 56, through the resistance 48, the conductor 51, and the second resistance 39, to the conductor III, and then to the conductor 30, back to the solenoid 25. Naturally this current is reduced by the two resistances 39 and 40 through which it is forced to flow.

The first pair of contacts to open is the pair of contacts 95, IM which introduces the resistance 39 into the circuit. The second pair of contacts to open is 55, I02, which forces the resistance 40 into the circuit and this increases the resistance and decreases the current. The choke valve 22 is thus progressively permitted to open by the eifect of the successive reductions inthe flow of current. When the contact 52 moves to the right and opens the contacts 4|, 52, then the entire mechanism is disconnected and the choke valve 22 isfree to open without any resistance from the solenoid. If, before the contacts 4|, 52 open, that is, during the starting operation, the engine begins to stall and the vacuum in pipe 21 is destroyed, then some vacuum will linger in the chamber I08. The efitect of this vacuum is to maintain connection between the contact 38' and the terminal I04, and to momentarily engage the contact 38 with th stationary terminal 53. This short-circuits the resistances 39 and 48, and thus sends a powerful current through the solenoid 25 and momentarily closes the choke valve 22 and thus checks the tendency of the engine to stall; The same effect results from a sudden opening of the throttle I82, destroying the vacuum'in the chamber I88 located in the housing 59.

It will thus be seen that when atmospheric pressure exists in the pipe 21, a very powerful current flows through the thermostatic metal 34, down through the conductor 56, through the conductor I0 and through the contact 38, and the stationary terminal 53. The moment the engine fires, the contact 38, 53 is opened. This current is successively weakened by the successive openings of the contacts first 95, ml, then 55, I02, and finally, 52, 4|.

The thermostatic metal 94 is set to open its contact 95 at 48 F.

The thermostatic metal 35 is set to open its contact 55 at 85 F.

The thermostatic metal 34 is set to open its contact 52 at 138 F.

The resistances '39, 40 are adjusted to give the necessary reduction in current for these temperature increases. The heating coil 98 is set to give the correct time effect.

I claim: i

1'. Automatic starting means for an internal combustion engine having -an electric circuit, external carbureting means, a mixture outlet leading therefrom and an air entrance leading thc:eto comprising a valve mounted in said ain entrance, means responsive to the air flow through said entrance for opening said valve, a solenoid electrically connected to said circuit and having a core mechanically connected'to said valve so as to close the same when said solenoid is energized by said circuit, a temperature responsive switch mounted on said engine for opening said circuit when the enginereaches a predetermined temperature, a resistance in said circuit between said switch andsaid solenoid, a second switch in said circuit located between the first switch and the solenoid so as to short-circuit said resistance when closed, a vacuum chamber having a passage connected to said mixture outlet, a restriction therein, means responsive to the temporary difference of pressure in said chamber and said mixture outlet for holding said second switch closed until the pressure in the chamber becomes substantially equal to that in the mixture outlet, resilient means for opening said second switch at all times except when the vacuum in the mixture outletis less than that in the chamber.

2. Automatic starting means as described in claim 1 together with a second temperature responsive switch mounted on said engine and located in said electrical circuit so as to shortcircuit said resistance when cold, a second resistance in said circuit, a third temperature responsive switch mounted on said engine and located in said circuit so as to short-circuit said second resistance when cold, a heating coil located between the second and third temperature responsive switches and grounded at one end and connected to the circuit through a fourth switch at the other, means for applying mixture outlet vacuum to operate said fourth switch so that the heating coil is in operation so long as there is vacuum in the mixture outlet.

3. Automatic starting means as described in claim 1 together with a second temperature responsive switch mounted onsaid engine and located in said electrical circuit so as to shortcircuit said resistance when cold.

4. Automatic starting means as described in' claim 1 together with a second temperature re cated in said circuitso as to short-circuit said second resistance when cold.

5. Automatic starting means for an internal combustion engine having a source of electricity,

an electric circuit connected thereto, external carbureting means, a mixture outlet leading" therefrom and an air entrance leading thereto comprising a valve mounted in said air entrance, means responsive to the air flow through said entrance for opening said valve, a solenoid electrically connected in said circuit and having a movable core mechanically connected to said valve so as to close the same when said solenoid is energized'by said circuit, a pluralityof temperature responsive switches mounted in said en-'- gine, a plurality of'resistances in said circuit, each of said switches being adapted to shortcircuit one of said resistances at different temperatures whereby the flow of current permitted to flow to said solenoid is reduced step by step as the temperature increases.

6. Automatic starting means as described in claim 5 in which a heating coil is located adjacent to one of said temperature responsive switches and connected to said circuit througha switch, means responsive to an increase of vacu um in'said mixture outlet for moving said switch to render said heating coil operative.

7; Automatic starting means as described in. claim 5 in which an additional switch is provided adapted to short-circuit at least one of said resistances, a vacuum chamber communicating 4 

